Furnace muffle construction



Nov. 2, 1943. R. F. RENKIN 2,333,579

` FuRNAcE MUFFLE CONSTRUCTION Filed May 2s, 1942 y:a sheets-sheet 2 Patented` Nov. 2, 1943 UNiTEo s Ares i A FURNACE Muerta ooNs'raUo'rreN' Robert F. Rankin, Sharon, Pa., assignorvoi one# half toHeru'yl A. Roemer, llittsburgliPa. i

,4 Claims.

` The invention relates lgenerally to an improved construction for an elongated furnace muiiie, and more particularly to removable means for supporting a continuous steel strip or the like passing through the muiiie of a gas pickling furnace.

In coating steel products, and more particularly, in coating steel strips, wire and the like desirable to eiect the cleaning by means of a dry pickle treatment instead of the ordinary wet pickle treatment. A method of coating steel wire or strips including such dry pickle treatment is set forth in my prior Patent Ne. 2,245,225. issued June 10, 1941. p

In subjecting the product (for example steel strip) tobe coated to this dry pickle treatment, it is passed through a long closed muille tube located within a heating furnace, and a heated controlled active atmosphere or pickling gas is passed through the muile'tube, preferably Yin a direction counter to the travel of the strip. This pickling. gas is adapted for reacting with the scale and other surface impurities on the strip to form gases or vapors which are carried oil' with the pickling gas passing through the muie. However, a certain proportion oi these reaction products form a deposit which accumulates on the bottom of the mufile tube and which must be removed at intervals.

The mu'iile tube must be of low height so that the pickling gas passing therethrough will be kept close to the strip, and preferably bames or deectors depend `at intervals from the top of the muiiie tube and terminate close to the top surface of the strip for directing the pckling gas against the top of the strip. Also spacer supports must be provided on the bottom of the muiile tube for raising the strip above the bottom of the muilie tube to allow the pickling gas to circulate freely under the strip and in contact with its under surface.

In prior gas pickling furnace constructions known to me, these spacer supports have been in the form of longitudinally' spaced transverserows of ngers secured to and projecting upwardly V from the bottom of the muille tube, the :lingers of each row being desirably staggered with respect to thejngers of adjoining rows.

Such fingers function very well at rst -to keep the strip raised and allow the gas to circulate reaction products of the-,gas with' the scale and n impurities' removed :from lthe strip accumulate on thev bottom oi the muiiie `tube to such an ei:- tent as to require cleaning out. j p

Due to the fact that atypical mume tube for a gas pickling furnace may vv*be upwards oi fifty reet longwitha inamum inside heightof about six inches for an inside width of about thirty inches and with vthe rdepending-pattes terminating about one inchabove the tops vof the spacer rlngers, itis almost impossible'to clean out the accumulated deposit on the bottom of the mulile and lbetween the fingers without removing the muiiie tube from the furnace and tearing it down, and this condition is'all the more aggravated because of the fingers being staggeredf 'A Consequently, in order tothoroughl'y clean out the :nume in such a furnace, it is necessary to remove it entirely from the furnace' and to tear it clown, and even though the :nume is made u p of sections bolted together and supported yin. the furnace on rollers, the sectionsare necessarily heavycastings of heat resistant metal, so that their removal from .and .replacement in a furnace struction for an elongated furnace mufiie, which permits cleaning out the rhume without disturbing its position in the furnace. 1 i

Another and more specinc object is to provide novel means removable as a unit, for supporting a strip in spaced relation to the bottom of an elongated munie.

able bottom for an elongated muie.

A still further object is to provide a novel removable bottom plate substantially coextensive A further object is to provide av novel removin width and length with the mufiie, and'having al1 of the foregoing objectives and which reduces lto a. minimum theftime "and'labor involved in cleaning out a muflie.

spacer supports secured thereto for supporting the strip in spaced relation to said plate.

And inally,l it is an object to provide a simple and inexpensive construction which accomplishes These and other objectsare accomplished by the parts, structures, arrangements and combinations comprising the present invention, a pre- Aferred embodiment of which is disclosed in the accompanying drawings and hereinafter described in detail. Y

While I have shown the invention as applied to the coating of strip steel, by way of example, it will belunderstood that the invention includes av construction to be used in the coating of other steel products such as sheets. strip sheets, rods or wires, without departing from the scope of the appended claims.

Referring to the drawings forming part hereof,

Figure 1 is a fragmentary plan sectional view of a gas pickling muilie furnace embodying the 1o present invention Fig. 2 is a longitudinal sectional view thereof;

Fig. 3 is a fragmentary enlarged transverse' l sectional view as on line 2-2 Fig. 1;

Fig. 4 is an enlarged fragmentary `view similar 15 toFig.2; and

Fig. 5 is a further enlarged fragmentary detached isometric view of the improved removable bottom plate for the muliie.

Similar numerals refer to similar parts p0 throughout the several views of the drawings.

The gas pickling furnace shown by way of example in the accompanying drawings is adapted to continuously 'clean the surface of steel strip to prepare it for being coated with zinc after it passes through the pickling furnace.

Referring to Fig. 2, the steel strip 8 isshown passing through the gas pickling furnace in the direction of the arrow, and the strip is enclosed during all of its travel through the furnace by an elongated muIlle tube indicated generally at 0.

The furnace is indicated generally at 1V and is of usual construction having the refractory side walls I, end walls 9 and I0, and arched roof wall II. The furnace hearth is made up of refractory checker work supported on the bottom wall-I2 of the furnace, and forming a series of transverse heating chambers indicated at I2 into which suitable burners I4 (Fig. 3) are directed, preferably at opposite ends of alternate chambers, for heating the interior of the furnace. y

Ine-order to obtain the most effective cleaning or pickliiig action from the gas circulated within the muille tube i, the furnace should be maintained at a temperature of about l2 00 to 1250" 45 F. The pickling gas is preferably a mixture vof gases including air, natural gas and chlorine in certain definite proportions, depending upon the capacity of the furnace, and the pickling gas is preferably circulated through the munie in a direction counter to the flow of the strip. f

As shown in the drawings, the pickling gas is introduced into the discharge end of the munie through the inlet pipes I5 and is discharged from the muiiiethroughthe downtake outlet pipes I8 55 communicating with the sides of the muille near its entrance end by.means of ports indicated at I1. Preferably the outlet pipes I6 extend downwardly through the furnace and through a water seal (not shown), and a vertical pipe I9 'is pref- 60 erably provided extending upwardly from the mullie above each outlet pipe IS, and provided with a peep hole 20 at the top thereof.

The elongated muifle tube is preferably supported within the furnace chamber at longitudinal intervals by means of rollers 2 I which rolle ably support beams 22 carried on the underside of the muiiie tube. The muilie tube 6 is preferably made up of a number of tubular sections, which are bolted together at joints 23 and welded 70 together at other joints 24. Preferably, the elongated munie tube is provided with depending baille portions indicated at 2i, at longitudinal intervals, for deflecting the pickling gas flowing through the munie tube downwardly against the upper surface of strip S passing in the opposite direction therethrough. As shown in Fig. 2, sealing plates 26 may be secured to the entrance end of the muilie above and below the strip in any suitable manner in order to prevent leakage vof the pickling gas at that point. Suitable sealing means may also be provided beyond the gas inlet pipes I5 to. prevent the escape of the pickling gas at the discharge end of the munie.

The improved removable bottom plate for the elongated mume is best shown in Figs. 4 and 5,

the sealing plates 26 having been removed in Fig. 4. The bottom plate 21 is preferably 18-8 stainless strip about .05|" thick, and is substantially co-extensive with the bottom wall 28 of the muffle. As shown in Figs. 1, 2 and 4, the bottom' plate 21 extends from the entrance end 29 of the mullle tube to a point adjacent to the inlet pipes II at the discharge end of the munie. The bottom plate 21 is provided with rounded spacer supports 3l and 3l secured as by welding indicated at 20a to its upper surface, and preferably staggered longitudinally of the bottom plate. These supports may be half sections of nickelchrome cast pipe in order to be heat resistant, and support the moving strip S in spaced relation to the bottom plate with a minimum of friction.

As shown in the drawings, the bottom wall of the mulile tube 6 is provided at the outlet ports I1 with an upwardly projecting hump or raised portion 32, but the bottom plate 21 is of such thin flexible material as to easily curve over the hump 32, as indicated at 33 in Fig. 4.

Thus,.as the pickling gas enters the muflleftube 6 through the inlet pipes I5, it is deflected downwardly onto the top surface of the strip at each of the depending baiiles 25, so as to follow a somewhat sinuous path between the top wall of the muilie tube and the strip, and the gas passing under the strip between the strip undersurface and the bottom plate21, follows a somewhat sinuous path through the staggered spacer supports 36 and 3l to the discharge ports I1. l

After the strip has been run through the muille 6 for some time, the reaction products of the pickling gas with the iron oxide scale and other lmpurities such as oil, dirt, lime and grease on the surface of the strip, gradually form an accumulated deposit on the bottom plate 21, which must be cleaned out from time to time in order to have the gas circulate properly. If the removable bottom plate 21 were not present and the spacer supports were secured directly to the bottom wall 28 of the munie, as is the case with prior constructions, the only way the muiile tube could be cleaned out would be to reach in with an extremely long handled tool and pull or scrape out the foreign matter. However, if such spacer sup` ports were staggered, as is customary and desirable, such method of cleaning out is precluded and the only thing left to do is to completely remove the muilie tube from the furnace and take it apart to clean the same.

With the present improved construction, all that is necessary to completely clean out the muflie tube is to remove the sealing plates 26, take hold of the end of the bottom plate 21, which is then easily accessible as shown inFig. 4, and then pull out the whole bottom plate endwise with its spacer supports secured thereon, through the entrance end ofthe muille tube. The bottom plate 21 collects substantially all of the accumulated foreign matter in the mulile and is easily vals from the top of said muille tube and terminating closely adjacent to said strip, and an endwise removable bottom plate carried on and substantially coextensive with the bottom wall of said muiile tube, said bottom plate having upwardly projecting longitudinally staggered spacer supports for supporting the strip in spaced relation to saidbottom plate.

2'. Muiiie construction for a gas pickling furnace including an elongated mume tube of low height extending continuously through the iurnace and adapted for enclosing a metal strip passing therethrough, and an endwise removable bottom plate carried on and substantially coextensive with the bottom wall of said mume tube, said bottom plate having upwardly projecting longitudinaliy staggered spacer supports for supporting he strip in spaced relation to said bottom -Pla 3. Muiiie construction for a gas pickling furnace including an elongated muilie tube of low height extending continuously through the furnace and adapted for enclosing a metal strip passing therethrough, haiiles depending at intervals from the top of said munie tube and terminating closely adjacent to said strip, and an endwise removable bottom plate carried on and substantially coextensive with the bottom wall of said muiiie tube, and rounded spacer supports secured to the upper surface oi said bottom plate at longitudinally staggered locations for supporting the strip in spaced relation to said bottom plate while permitting gas to circulate between the bottom plate and the strip. l

4. In an elongated tubular muiiie for gas treating a strip enclosed therein, a bottom plate movably supported on the bottom vwall of the muilie and removableendwise therefrom, said bottom plate having upstanding supports secured thereto at longitudinal intervals for supporting said strip ROBERT F. RENKIN. 

